Stuart Gulliver, chief executive of HSBC, has withdrawn as a speaker at an Olympic investment conference where he was due to share a podium with the bank's embattled former chairman Lord Green.

He was due to appear on Thursday with Green, the trade minister who is under fire over his tenure at HSBC when it laundered money for Mexican drug barons and broke sanctions. The Business is Great Britain event has been billed by the government as the UK's "biggest ever" investment conference and it takes place on the eve of the Olympic Games' opening ceremony.

Labour is piling pressure on Green to explain what he knew and when about the findings of last week's damning US Senate report, which criticised HSBC for allowing money laundering to take place from 2004 to 2010. Green and Gulliver had been due to make the opening remarks side by side at the conference, which the bank is also sponsoring.

It will be one of a series of business summits taking place during the Games, at which Green is scheduled to take an active role. While Gulliver will no longer be speaking, he is expected to attend and mingle among the high-profile delegates who include Christine Lagarde, head of the International Monetary Fund, and Sir Mervyn King, Bank of England governor. Cabinet ministers are also speaking at the event, which is intended to showcase the UK as a place to do business.

A government spokesman defended the decision to maintain HSBC as a sponsor: "We're going to be putting on a world-class event and have to do it with value for money in mind." It had previously been reported that Barclays was sponsoring the event but is no longer doing so since the Libor manipulation scandal.

Gulliver had only been brought in at the last minute following the withdrawal of Bob Diamond, who resigned as chief executive of Barclays this month. HSBC is now a sole sponsor.